Computed Tomography Algorithms for Helical Scanned Data

The revolution in digital processor and memory technology is making it feasible to execute Computed Tomography, CT, at much higher rates. Use of multiple fixed sources eliminates the rate limitation of mechanical scanning. The final limit to accurate CT scanning of objects in rapid continuous motion is artifacts produced by different projection planes through the object. Methods of minimizing the effects of plane offsets are defined. They include interpolation between sequential scans and maximum likelihood weighting to maximize the consistency of the reconstruction. The improvement of these techniques over straightforward reconstruction of projections in differing planes will be quantified. An Algebraic Reconstruction Technique is used that can accommodate any source-detector geometry. X-rays are the most common method of noninvasive internal inspection. Rapid, economical, accurate CT scanning will greatly facilitate all types of X-ray inspection now used and make many more feasible. Some examples are parts and assembly inspection, inspection of injection molds, and composite materials for voids, and inspection of machines, plumbing and pressure vessels, and bulk materials for cracks, voids, or adulteration.